NITRIC-OXIDE RELAXES RABBIT CORPUS CAVERNOSUM SMOOTH-MUSCLE VIA A POTASSIUM-CONDUCTIVE PATHWAY

We tested the hypothesis that acetylcholine-induced relaxation in cave rnosal tissue is the result of nitric oxide production that alters Kconductance. In the organ bath, acetylcholine- and sodium nitroprussid e-induced relaxation of corpus cavernosum were significantly attenuate d by tetraethylammonium. Basal [K+](i) in cavernosal smooth muscle cel ls was 102 + 11 mM using a K+-sensitive fluorescent dye. Acetylcholine produced a decrease in [K+](i) to 74 +/- 10 (n > 4, P < 0.05). Tetrae thylammonium pretreatment blunted the acetylcholine- and sodium nitrop russide-induced decrease in [K+](i) by 82%, (n > 5, P < 0.001), respec tively. L-NMMA blunted the acetylcholine- and sodium nitroprusside-ind uced fall in [K+](i) by 93% and 83% (n > 4, P < 0.001), respectively. These data suggest that acetylcholine-mediated cavernosal smooth muscl e cells relaxation occurs through nitric oxide release with activation of K+ conductance. (C) 1996 Academic Press, Inc.